1. The Field of the Invention
The present invention relates generally to devices for high speed data transmission. More particularly, embodiments of the invention concern optoelectronic devices having one or more intelligent transmitter modules and specialized functionality.
2. The Relevant Technology
Computing, telecom and networking technology have transformed our world. As the amount of information communicated over networks has increased, high speed transmission has become ever more critical. Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications ranging from modest Local Area Networks (“LANs”) to backbones that define a large portion of the infrastructure of the Internet.
Typically, data transmission in such networks is implemented by way of an optical transmitter, such as a laser or Light Emitting Diode (“LED”). The optical transmitter emits light when current is passed through it, the intensity of the emitted light being a function of the magnitude of the current. Data reception is generally implemented by way of an optical receiver, an example of which is a photodiode. The optical receiver receives light and generates a current, the magnitude of the generated current being a function of the intensity of the received light.
Various other components are also employed by the optical transceiver to aid in the control of the optical transmit and receive components, as well as the processing of various data and other signals. For example, such optical transceivers typically include a driver (e.g. referred to as a “laser driver” when used to drive a laser signal) configured to control the operation of the optical transmitter in response to various control inputs. The optical transceiver also generally includes an amplifier (e.g. often referred to as a “post-amplifier”) configured to amplify the channel-attenuated received signal prior to further processing. A controller circuit (hereinafter referred to as the “microcontroller”) controls the operation of the laser driver and post-amplifier. A clock and data recovery circuit (hereinafter referred to as the “CDR”) may also be used in telecommunication applications (e.g., SONET networks) to equalize and retime electrical data signals prior to transmission as optical signals.
Two often conflicting demands in the market for components used in optical networks are the demands for higher transmission speeds and miniaturization. The conflict is evident, for example, in trying to design modules suitable for use in SONET applications that can also achieve 10 G and above telecommunication data transmission speeds. The high-speed nature of signal transmission demands a minimum number of electronic interconnects with a short path for electrical transmission between the components of the module. Electronic interconnects in the form of leads, flex circuits, and piece-wise continuous ground connections pose a major challenge in meeting SONET jitter performance due to reflections and bandwidth limitations. Electromagnetic compliance on the transmit side (e.g., CDR, laser driver, transmitter) is also a major challenge due to high frequency signal generation and reflections at each interface, which can be major sources of EMI emissions at 10 G data rates.
The current dominant technology for achieving long haul (>80 km) optical transmission at and above 10 G data rates implements Lithium Niobate Mach-Zehnder and InP Mach Zehnder modulators. Typically, however, modules implementing this technology are relatively expensive, large, and power hungry. One alternative solution for achieving 10 G data rates in applications less than 100 km involves the use of directly modulated lasers (“DMLs”) or externally modulated lasers (“EMLs”), which are often less expensive, smaller and less power hungry than Lithium Niobate Mach-Zehnder and InP Mach Zehnder modulators. However, adiabatic chirp generated in distributed feedback lasers due to RF pickup and back reflection and transient chirp in the modulator section cause rapid distortion of the eye after fiber propagation. As a result, conventional DMLs and EMLs remain limited to applications less than 100 km.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.